Currently, the return type of getChildren() is java.util.List<Component>
But if we want to do the follow cast, it will cause compile error.
List<Listheader> headers = (List<Listheader>)head.getChildren();

Could you change the return type to List<? extends Component> ?
It should retain the generic quality, and solve the problem above.
And we also ask you to change all methods that generic like this.
Thank you!